|Bore / Stroke||40.0mm x 39.2mm|
|Horsepower||7 horsepower @ 8,800 RPM|
|Torque||0.59 kg-m @ 8,500 RPM|
|Fuel System||Carburetor, Mikuni VM16SH|
|Spark Plug||NGK B8HS '87-93|
|Battery||YUASA 6N4-2A-2 '87-93|
|Transmission||5-speed constant mesh|
|Final Drive||Chain: 420x100|
|Front Tire||3.50-12 '87-93|
|Rear Tire||4.00-12 '87-93|
|Related||Yamaha RX50 (contained same engine), Yamaha YSR80|
|Competition||Honda NSR50, Aprilia RS50|
This style of miniature motorcycle is known as a pocket bike. Although small in size, these machines are capable of giving surprising performances in the hands of skilled operators. Enthusiast groups organize races and endurance runs for pocket-bikes, of which the YSR Yamaha is the most popular. It mainly competes with the likes of the Honda NSR50. The limited edition Yamaha RX50 shared the same engine.
Yamaha YSR 50 and YSR 80 sport models goes on sale in Japan in 1986, and had the look of a re-shaped, scaled-down YZR500 factory racer that appealed to the spirit of race enthusiasts. The 2-stroke single-cylinder engine had a maximum output of 7 ps for the 50cc and 8.8 ps for the 80cc, a return type 5-speed transmission, front disc brake and other features to offer full-fledged sport riding potential. It became a standard in the mini-bike races popular at the time. 1992 was the last year of production, and the price was 189.000 yen for the 50cc and 211.000 yen for the 80cc.